2312 W CASINO RD 2025-07-25 - Laserfiche WebLink

I Basic Treatment The filter media cartridges are sized based on an approved flowrate capacity per canister,as established by the WSDOE and the manufacturer's recommendations. A treatment capacity of 7.5 gpm is used to meet the WSDOE's General Use Level Designation of allowing 1 gpm/square foot of media treatment and applying it to the 18-inch standard filter that is provided by Contech Stormwater Solutions. p Water Quality Flowrate 15.3 gpm Y Treatment Capacity - 7.5 gpm/cartridge trit� `U I Required No. of Cartridges = 2.0 cartridges - C (ts) Based on this calculation,two cartridges will be provided. ii 164, 2300 Kasch Park Road Property ' 4, , f EXISTING CONDITIONS �', , The existing Community Transit Kasch Park Operating Base is being used as a bus maintenance and storage base. A multi-phased Master Planning exercise that took place in 1993-1994 included development of a storm drainage runoff control system to manage a full.operating base build out. The entire parcel consists of 20 acres. The Master Plan accounted for a full build-out of 13.1 acres of impervious area and 5 acres of pervious,and the remainder as wetlands and wetland buffer. The stormwater system -r r'' includes catchbasins and conveyance pipe,which collect site runoff and direct it to a flow splitter �; leading to an oil/water separator or directly to the detention vault. The detention vault has been size ,offor the 13.1 acres of impervious surface and 5 acres of pervious. From the outlet of the flow control .0 for the detention system,the full two-year release rate is pumped up to a bioswale to provide water quality treatment. The outlet to the bioswale and the remaining detention system discharge to a culvert in the far south east corner of the site. The stormwater controls were sized and built for the areas listed above. Currently,the site consists of only 12 acres of impervious surface, rather than the full 13.1 acres of impervious surface for which the system was designed. REDEVELOPED CONDITIONS Site redevelopment at the existing Operating Base consists of regrading and paving of an existing parking lot. The existing parking lot is currently asphalt paved and includes stormwater catchbasins and conveyance piping that connect this area to the on-site stormwater runoff controls mentioned above. The parking area is currently sloped up to 10 percent, and Community Transit desires to re-grade it to approximately 2 percent slope and pave it in concrete to allow buses to be parked there. The area impacted is approximately 0.45 acres and is 100 percent impervious. In addition to the parking area,there will be minor grading to the area surrounding the new bus wash building. This will require removal of approximately 2,585 square feet of existing concrete pavement to accommodate regrading and utility trenching prior to repaving with concrete. Community Transit Kasch Park Operating Base 3